New per se limit in Washington is problematic

As things now stand, if a driver is suspected of driving under the influence of marijuana the prosecutor must prove that the driver had lost the normal use of his mental or physical faculties due to the use of marijuana. The decision is then left in the hands of the jury to determine whether or not the state proved up its case.

On December 6 that will change. Instead of relying on a drug recognition evaluator to give his opinion on whether or not Johnny is hopped up on too much weed, the state can look to the results of a blood test.

Should a driver show a concentration of THC greater than 5 nanograms, he or she will be considered per se under the influence - in much the same manner as a driver with an alcohol concentration of greater than .08 grams per 210 liters of breath. While there are scientific studies that purport to demonstrate that THC concentrations over a certain level correlate to impairment, the studies don't take into account the shortness of the "high" and the way in which the body stores THC.

The buzz one gets from marijuana comes and goes quickly. The THC, however, is stored in the body's fat cells for up to 30 days. This means that a fair amount of THC in the body may be inactive. In other words, a reading of 5 nanograms doesn't necessarily mean that a motorist is impaired.

While I understand those who wanted to create a per se limit for THC, I must fault their rush to create a number without taking into account the problems inherent in such an approach. For one, the battery of roadside exercises police use to make their arrest decisions in DWI cases have never been tested on people who have smoked marijuana.

Without the "rigorous" testing NHTSA conducted on their exercise protocol, we have no way of knowing what levels of THC concentration correlate to what levels of performance. Without that correlation, any per se limit is just a number grabbed out of a hat.

Such a set-up will only serve to deprive those accused of driving under the influence of marijuana of a defense to the charge, as the court will presume that a driver with a THC concentration of 5 nanograms or higher is under the influence. That presumption will be made with or without signs of impairment.

While the referendum in Washington is a good sign that folks are starting to think hard about the failures of the war on drugs and the futility of treating drug use as a criminal matter and not a public health issue, the creation of a new per se limit is a troubling reminder that junk science lives on.